Re: [CAD_CAM_EDM_DRO] Re: Major encoder trouble, need advice.

Henrik:

I see that you have checked the signals with your oscilloscope but you
didn't mention at which points you made the tests. Is there any difference in
what the signals look like at the encoder and what they look like at the other
end where they are input to your controller?

Did U.S. Digital specify twisted pair to be used with their encoders? I
have always used normal shielded cable, not twisted pair. Many of the encoder
manufacturers I have used actually specify twisted pair NOT be used, these are
much higher priced units that U.S. Digital and that may be the reason.

Another thing to keep in mind is to not attach both ends of the shield, only
connect one end of it to ground or the negative side of the power line, I
didn't see where you said how you had attached the shield.

Now, none of this may help but I thought I would put in my "two cents" worth.

Randy Abernathy
Industrial woodworking machinery installation, design, repair and servicing
Over 24 year experience with factory training
Fax: 770-974-5295
Phone: 770-974-5295


In a message dated 9/25/2008 5:29:46 P.M. Eastern Daylight Time,
henrik-olsson@... writes:

Hi Bill,
I have an oscilloscope and I have looked at the signals. Without power to
the motor the encoder signals looks very good, nice uniform, 50% dutycycle
and 90° phase shift. With motor powersupply turned on there IS noice on the
encoderlines, however, it doesn't look much different than it does with the
AMT encoder.

I also scoped the 5V 'rail' on the drive and I can see quite large
spikes/ringings there, especially during motor reversals. I'm not sure that
the trace I see correctly reflects the reallity but even if it does these
spikes does A: Not upset any of the other chips, like the ATMEL CPU and, B:
Create problems with the AMT or Hengtler encoder.

And now I even feed the encoder with an external 5V supply but it still
doesn't work so the any possible noice on the drives 5V-line probably isn't
the problem. (Or there's more than one problem.....)

Frustrating....

Thanks!
/Henrik.






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